Support R_ARM_REL32 and R_ARM_GOT_PREL in RuntimeDyldELF (SR-387)

Lang Hames via llvm-commits llvm-commits at lists.llvm.org
Thu Aug 18 18:25:16 PDT 2016


Hi William,

Daniel told me you were still hoping to land this, so I took a stab at
writing a test for it and discovered that, unfortunately, RuntimeDyldELF's
GOT building mechanism (which uses a separate section for GOT entries)
isn't compatible with RuntimeDyldChecker.

The proper solution to that is to fix RuntimeDyldELF's GOT handling (it's
not safe to use a separate section in general, as it may be allocated out
of range of a PC-rel GOT entry load), but that's non-trivial.

In the mean time, since this patch doesn't change any existing behavior
I've committed in r279182.

Cheers,
Lang.


On Tue, Mar 22, 2016 at 1:05 PM, Lang Hames via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Hi Michael, William,
>
> William - thank you very much for this!
>
> If possible, could you please add an ELF test case to
> llvm/test/ExecutionEngine/RuntimeDyld/ARM? There is an existing MachO
> test case there that may be of some help, though it does not contain any
> GOT relocation tests. From the x86-64 GOT test:
>
> # Test PC-rel GOT relocation.
> # Verify both the contents of the GOT entry for y, and that the movq
> instruction
> # references the correct GOT entry address:
> # rtdyld-check: *{8}(stub_addr(test_x86-64.o, __text, y)) = y
> # rtdyld-check: decode_operand(insn3, 4) = stub_addr(test_x86-64.o,
> __text, y) - next_pc(insn3)
> insn3:
>         movq    y at GOTPCREL(%rip), %rax
>
> The first test is reading the value of the stub (in this case GOT entry)
> for y and verifying that it contains the address of y.
> The second test is verifying that the PC-relative offset for the
> instruction is equal to the difference between the stub address and the
> next instruction.
>
> Cheers,
> Lang.
>
> On Mar 22, 2016, at 12:58 PM, Michael Gottesman <mgottesman at apple.com>
> wrote:
>
> I am not actually reviewing this, but just as a drive by: This is
> definitely going to need tests.
>
> On Mar 22, 2016, at 12:56 PM, Michael Gottesman via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
> Lang, can you take a look at this one?
>
> On Mar 22, 2016, at 10:59 AM, William Dillon via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
> <llvm.patch>This change supports the swift interpreter on armv7-based
> linux machines.  This is required for a number of tests and the package
> manager.
>
> - Will_______________________________________________
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